Several classes of molecules possess a structural pocket for the binding of adenosine triphosphate (ATP). Molecules that include a structural pocket for binding ATP include enzymes such as kinases, ATP binding cassette transporters, and myosin. ATP serves as an energy source for the catalysis of reactions through the cleavage of a high energy phosphate bond.
Protein kinases typically bind ATP in a binding pocket that resides in a structurally conserved catalytic domain. ATP binding, in conjunction with the inherent ability of protein kinases to bind small organic molecules, has made the ATP binding site of protein kinases a target of many small molecule protein kinase inhibitor drug discovery efforts. Several technologies have been developed to allow for the screening of protein kinase inhibitors. Many measure the inhibition of phosphorylation of a substrate by a protein kinase in the presence of a potential kinase inhibitor as the means of screening. While these technologies provide a read-out of kinase inhibition from a functional perspective, they may not measure binding and may provide little or no kinetic information.